Melamine resins and polyisocyanate compounds have been used as curing agents for thermosetting paints but they showed problems in chemical resistance, toxity to human body and the like.
In order to solve these problems, the use of blocked amines has been proposed, but it is difficult to obtains curable compositions having superior properties. For example, Japanese Kokai Publication (unexamined) discloses a hydraulic composition which comprises acid anhydride polymers and polyoxazolidines, but this composition is insufficient in chemical resistance and weather resistance and does not exhibit a superior finishing appearance.